DESCRIPTION: Sickle cell anemia is a multi organ system disease caused by the abnormal physical properties of HbS. HbS has the unique tendency to polymerize and distort RBC in the circulation, resulting in widespread vascular insufficiency. The polymerization (and sickling) tendency of HbS- containing RBCs is exponentially related to the concentration of HbS in the cell. Sickling itself causes the cell to lose water and KCL, further exacerbating sickling as cells become dehydrated. RBC Mg plays a central role in the control of cell water content, volume and membrane functions in normal and sickle RBCs. K-Cl cotransport, a system involved in dehydration of sickle RBCs, is markedly inhibited by increasing cell Mg. There are reports which claim that Mg content of dense fraction of SS cells may be decreased. Dietary intake of Mg in SS patients has not been studied. The specific aims of this proposal are the following: 1) Assess the dietary intake of Mg in patients with SS disease; 2) study the regulation of RBC Mg and the effects of Mg on ion transport and other membrane functions in normal and sickle erythrocytes and in genetically determined high Mg and low MG mouse erythrocytes; 3) assess the effect of dietary Mg supplementation in SS patients.